This invention relates to apparatus for applying light sensitive materials to semiconductor slices, and more particularly to a method and apparatus for simultaneously coating a plurality of semiconductor slices with photoresist material.
In the manufacture of various electronic devices there is first formed a large diameter slice comprising a particular semiconductor material, for example, N-type semiconductor type material such as silicon. Various diffusion and/or deposition processes are then employed to form regions of a different type semiconductor material, in this case P-type semiconductor type material, on the semiconductor slice. In many instances conductive leads are formed on the slice and are electrically connected to various regions formed thereon. Finally, the slice is separated into a plurality of discrete components.
At various stages in the manufacturing process it is necessary to etch or otherwise treat certain regions of the slice while preventing treatment of adjacent regions. This is typically accomplished by coating the slice with a photoresist material, exposing the photoresist material to light through an appropriate mask, and then removing portions of the photoresist material to provide access to the underlying regions of the slice. This facilitates treatment of the selected regions of the slice in accordance with the desired treatment procedure, such as etching, while preventing treatment of the adjacent regions of the slice.
Notwithstanding the widespread use of photoresist materials in the manufacture of electronic devices, the processes which have been used heretofore to apply photoresist materials to semiconductor slices have not kept pace with other advances in the industry. Thus, it has often been the practice to apply photoresist materials to semiconductor slices on an individual slice basis. For example, in accordance with one prior art procedure, photoresist material is poured or sprayed onto one side of a semiconductor slice, after which the slice is spun to distribute the photoresist material uniformly across the surface of the slice. The other side of the slice must then be similarly treated.
The present invention comprises apparatus for applying light sensitive materials to semiconductor slices which overcomes the foregoing and other problems long since associated with the prior art. In accordance with the broader aspects of the invention, a plurality of semiconductor slices are mounted in a fixture. Photoresist or other light sensitive material is then applied simultaneously to all of the slices in the fixture. Thereafter the fixture is rotated to obtain a uniform coating of light sensitive material on each of the slices.
In accordance with more specific aspects of the invention, the slice supporting fixture comprises a housing formed from an open material such as screening, etc. so as to facilitate both the coating of the slices with the light sensitive material and the removal of the light sensitive material from the slices during the spinning operation. Within the fixture there is mounted structure adapted to support the slices by means of point contact with the edge portions of the slices. This is advantageous in assuring coverage of the entire surface areas of all of the slices with light sensitive material.
Two embodiments of the invention are disclosed. In one embodiment the slice supporting fixture comprises a pair of hingedly interconnected half cylinders each having a plurality of sawtooth-shaped slice supporting members mounted therein. Semiconductor slices are received in the fixture between the teeth of the sawtooth-shaped members. The second embodiment comprises a cup-shaped slice supporting fixture having triangular-shaped slice supporting members mounted in it. This embodiment of the invention is particularly useful in coating broken semiconductor slices.
Also disclosed are two techniques for applying light sensitive material to the semiconductor slices. One technique involves dipping the slice supporting fixture and the slices mounted therein into a quantity of light sensitive material. In the other technique light sensitive material is sprayed through the slice supporting fixture and onto the slices mounted therein.